This invention relates to lubricants for ceramic bearing surfaces, particularly for high temperature applications.
Commonly used solid lubricants or solid lubricant additives are graphite, molybdenum disulfide, polytetrafluoroethylene, lead oxide, boron nitride, alkaline metal borates, arsenic thioantimonate, and the like. These solid lubricants have certain disadvantages, such as limited high temperature stability, hydrolytic instability, potential toxicity, inferior performance under high vacuum or high temperature, or undesirable by-products after exposure to high temperature.
Complex metal chalcogenides such as K.sub.2 MoOS.sub.3, K.sub.2 WOS.sub.3, Cs.sub.2 WOS.sub.3, and Cs.sub.2 MoOS.sub.3 have been described in the literature. King, U.S. Pat. No. 4,545,973, issued Oct. 8, 1985, found that such compounds possess desirable lubricating properties; however, due to their water solubility, such compounds have limited utility in lubricant applications because they can be leached out of the lubricants when, for example, condensed moisture comes in contact with the lubricants. King discloses complex metal chalcogenides having the formula: EQU Mp(M' O.sub.x A.sub.4 - x)m .multidot. nH.sub.2 O
where M is a metal selected from the group consisting of Mg, V. Mn, Fe, Co, Al, Cu, Ga, In, Bi, As, Ni, Zn, Cd, Sb, Sn and Ce; where M' is a metal selected from the group consisting of Mo and W; where A is S or Se; where x ranges from 1 to 3; where p is 1 or 2 depending on the oxidation state of M; where m ranges from 1 to 5 depending on the oxidation state of M; and where n ranges from 0 to 6.
We have found that the lubricating properties of certain cesium compounds are enhanced by silicon.
Accordingly, it is an object of the present invention to provide high temperature cesium-containing solid lubricants.
Another object of this invention is to provide a method for lubricating a ceramic bearing surface.
Other objects, aspects and advantages of the present invention will be apparent to those skilled in the art from a reading of the following detailed disclosure of the invention.